Add ITkPixelCabling package

Introduces the framework of a new package, ITkPixelCabling. For the moment, this contains a new ITkPixelOnlineId class, an ITkPixelCablingData class and the algorithm ITkPixelCablingAlg which fills the cabling data from a simple two-column (offlineId, onlineId) text file. Tests are included for all components. Tagging @okovanda, @sroygara, @carquin as interested parties